U.S. Pat. No. 4,035,070 discloses optical modulation apparatus for generating a structured charge-discharge pattern on a photoreceptor. Such apparatus produces a plurality of generally parallel, collimated radiation beams of uniform intensity from a single collimated beam input. The apparatus includes an optical cavity of a medium, generally transparent to the input radiation, and configured with opposite parallel surfaces to which uniform reflecting surfaces are applied. One of the surfaces is fully reflecting and the other is partially reflecting. Over the partially reflective surface is a continuously variable (wedge) filter. When a single collimated beam is injected into the cavity through a side thereof such that the beam is incident on the partially reflective surface, the beam will be reflected recursively between the surfaces. After each reflection from the partially reflective surface, the beam is less intense due to the transmission into the wedge of a fraction of the radiation incident on the partially reflective surface. The beams transmitted into the wedge are substantially parallel, but the intensity of the beam decreases in the direction of propagation of the multiple reflections.
The function of the optical wedge is to inversely attenuate the beams transmitted into the wedge so that each beam emerging from the wedge will have the same intensity. U.S. Pat. No. 3,711,188 discloses an optical system having a uniform fully reflective surface inclined relative to a uniform, partially reflective surface. An image of a device to be displayed is injected into the space between the mirrors and onto the fully reflective surface. Light incident on the last mentioned surface is multiple reflected between the surfaces producing a plurality of rays that emerge from the partially reflective surface and provide a display of the item. By reason of the inclined relationship between the two surfaces, the emerging light is not parallel and the intensity is not uniform.
Many applications exist for an optical manifold capable of creating a plurality of parallel, uniformly spaced beams of equal itensity or having a predetermined intensity ratio. The '070 patent described above discloses a technique for achieving a plurality of parallel beams of equal intensity, but such technique is not efficient by reason of the attenuation of the transmitted beam introduced by the optical wedge. Furthermore, the wedge will introduce some non-uniformity in the spacing of the emerging beams. More importantly, however, it is not possible to change the number of exiting beams in the '070 patent except by varying the angle of incidence of the input beam. In so doing, however, the intensity of the exiting beams will become non-uniform.
It is therefore an object of the present invention to provide a new and improved collimated beam manifold wherein the above described limitations and deficiencies in the prior art are overcome or substantially reduced.